Optimization of region‐of‐interest sampling strategies for hepatic MRI proton density fat fraction quantification

Abstract

BACKGROUND Clinical trials utilizing proton density fat fraction (PDFF) as an imaging biomarker for hepatic steatosis have used a laborious region-of-interest (ROI) sampling strategy of placing an ROI in each hepatic segment. PURPOSE To identify a strategy with the fewest ROIs that consistently achieves close agreement with the nine-ROI strategy. STUDY TYPE Retrospective secondary analysis of prospectively acquired clinical research data. POPULATION A total of 391 adults (173 men, 218 women) with known or suspected NAFLD. FIELD STRENGTH/SEQUENCE Confounder-corrected chemical-shift-encoded 3T MRI using a 2D multiecho gradientrecalled echo technique. ASSESSMENT An ROI was placed in each hepatic segment. Mean nine-ROI PDFF and segmental PDFF standard deviation were computed. Segmental and lobar PDFF were compared. PDFF was estimated using every combinatorial subset of ROIs and compared to the nine-ROI average. STATISTICAL TESTING Mean nine-ROI PDFF and segmental PDFF standard deviation were summarized descriptively. Segmental PDFF was compared using a one-way analysis of variance, and lobar PDFF was compared using a paired t-test and a Bland–Altman analysis. The PDFF estimated by every subset of ROIs was informally compared to the nine-ROI average using median intraclass correlation coefficients (ICCs) and Bland–Altman analyses. RESULTS The study population’s mean whole-liver PDFF was 10.1±8.9% (range: 1.1–44.1%). Although there was no significant difference in average segmental (P=0.452) or lobar (P=0.154) PDFF, left and right lobe PDFF differed by at least 1.5 percentage points in 25.1% (98/391) of patients. Any strategy with ≥ 4 ROIs had ICC >0.995. 115 of 126 four-ROI strategies (91%) had limits of agreement (LOA) <1.5%, including four-ROI strategies with two ROIs from each lobe, which all had LOA <1.5%. 14/36 (39%) of two-ROI strategies and 74/84 (88%) of three-ROI strategies had ICC >0.995, and 2/36 (6%) of two-ROI strategies and 46/84 (55%) of three-ROI strategies had LOA <1.5%. DATA CONCLUSION Four-ROI sampling strategies with two ROIs in the left and right lobes achieve close agreement with nine-ROI PDFF. Level of Evidence 3 Technical Efficacy Stage 2

3D Multi-Echo Dixon technique for simultaneous assessment of liver steatosis and iron overload in patients with chronic liver diseases: a feasibility study

“…Observer 1 measured the parameters twice in a subset of 40 randomly selected patients (23 men and 17 women) from the study cohort to assess intra-observer agreement, and the interval between the data measurements was 7 days. As recently shown by Hong et al (11), Four-ROI sampling strategies can achieve a close agreement with sampling all nine ROI hepatic segments. Average values of the four ROIs were used as a representative value of liver for each patient, and then the mean value of the two observers was used for statistical analysis.…”

“…Sofue et al (43) showed that MRI-PDFF and R2* were repeatable between examinations. Hong et al (11) demonstrated that four-ROI sampling strategies with two ROIs in the left and right lobes achieve a close agreement with nine-ROI PDFF. In this study, we used the average value of four ROIs as a representative of the whole liver.…”

“…With recent advances in MR technology, several MRI-based approaches have been developed for liver fat (e.g., signal fat fraction using phase-encoding GRE or frequency-selective approach, PDFF using multi-echo chemical shift-enoded or magnetic resonance spectroscopy) and iron quantification (e.g., signal intensity ratio, T2/R2 relaxometry, T2*/R2* relaxometry). The PDFF is now generally accepted as the standardized imaging biomarker of liver fat (5,(10)(11)(12). Additionally, the correction of T2* decay by acquiring more echoes is necessary for accurate computation of MRI-PDFF.…”

Sample strategies for quantification of hepatic fat fraction mean MRI in healthy cats during body weight gain

“…Four ROIs sampling strategy (in the anterior, posterior, medial, and lateral segments) has been recommended in human medicine as a reasonable compromise between reproducibility and repeatability, and time invested in the image analysis [39]. This technique also achieved close agreement with the 9 ROIs technique [40]. Four ROIs strategy is also highly reproducible, with ICC >0.9 [38,40].…”

Now is the time to start routinely using chemical shift imaging in the spine

“…The application of out-of-phase techniques revolutionized the work-up of these lesions and allowed many more lung cancer patients to undergo curative treatments [3]. With the global epidemic of diabetes, the study of liver fat fraction became increasingly important, and chemical shift techniques are currently the norm in the study of chronic liver disease by MR [4].…”